ES2742831T3 - Apparatus and method for determining reference elements of an environment - Google Patents

Abstract

A method for determining reference elements of an environment to associate a predetermined map with a map of the environment in real time, the method comprising at least the steps of: providing a ceiling value and a floor value, these values corresponding respectively to a virtual or real ceiling (31) and a virtual or real floor (32) in the environment (2); - measuring, using a distance measurement sensor (10), sets (40) of positions of points in the environment, each of said positions comprising at least a first coordinate along a first direction (X) and a second coordinate along a second direction (Y) not collinear with the first direction (X), where each set (40) of neighborhood point positions is aligned along a straight line (41); - determining reference elements and non-referential elements of the environment, each reference element comprising a set of positions of reference points of the environment, said set of positions of points of the environment comprising at least one position of a set (40) of positions of environment points * whose second coordinate is strictly less than the ceiling value and strictly greater than the floor value, and * whose distance to the distance measurement sensor, taken along the first direction, is the greatest distance in a set of distances from said set (40) of points in the environment to the distance measurement sensor, where said distances are taken along the first direction (X), said non-referential elements corresponding to positions of a set ( 40) of positions of points in the environment, whose distance to the distance measurement sensor, taken along the first direction (X), is not the distance greater in a set of distances from said a set of points in the environment to the distance measurement sensor, where said distances are taken along the first direction (X).

Description

DESCRIPTION

Apparatus and method for determining reference elements of an environment

Field of the Invention

The present invention refers to a method and an apparatus for determining reference elements of an environment using a distance measuring sensor.

Background of the invention

Mobile robots, and especially autonomous or semi-autonomous mobile robots, often have to face the problem of positioning themselves in a new or changing environment for which a predetermined map is not available. To overcome this difficulty, simultaneous location and mapping algorithms (SLAM) have been developed and these can be used to construct a map of the surroundings of a robot in real time and to calculate a location of the robot based on this Map.

In SEO-YEON HWANG ET AL: "Monocular Vision-Based SLAM in Indoor Environment Using Corner, Lamp, and Door Features From Upward-Looking Camera" describes a monocular SLAM that simultaneously uses corner, lamp and door features to achieve navigation Stable in various environments. EP 2058720 describes a method for generating a map in three dimensions using structured light emitted by a robot towards a ceiling.

However, this solution has a number of disadvantages.

In particular, the interaction of a semi-autonomous robot with a human operator often involves the use of a predetermined map of the environment, which the operator uses to guide the robot or to indicate a specific destination to the robot.

Unfortunately, this default map often differs from the environment map generated by the robot in real time. These differences can, for example, arise from non-referential elements such as boxes, furniture, doors or the like that can move or can change their appearance over time and thus prevent the robot from being able to associate the default map with the map. of the environment.

The present invention is primarily intended to improve this situation.

Summary of the Invention

For this purpose, a method according to claim 1 is proposed.

In this way, non-referential elements can be identified with a high probability.

This may, among other things, allow a robot to associate a predetermined map with a real-time environment map, improve the calculation of a path from one point to another on a map, and operations in a changing environment.

In some embodiments, one or more of the following features could also be used:

- the first and second directions are perpendicular, said second direction corresponding to a vertical direction of the environment,

- the determination stage includes at least the operations of:

define a set of point positions within the set of point positions in the environment whose second coordinate is strictly less than the ceiling value and strictly than the floor value; calculate, for each point position in a set of point positions, a distance, taken along the first direction, which separates each point from the distance measurement sensor, to obtain a set of distances; and

identify a set of positions of reference points of the environment corresponding to the positions of the set of positions of the interior points, whose distance is the greatest distance in the set of distances.

- the determination stage is repeated for a plurality of first addresses.

- the distance measuring sensor comprises a laser,

- the first coordinates of a set of point positions are grouped with a first crush interval.

- the second coordinates of a group of point positions are grouped with a second grouping interval.

According to another aspect, an apparatus according to claim 8 is provided.

In accordance with yet another aspect of the invention, a mobile robot comprising the above mentioned apparatus is provided.

In accordance with yet another aspect of the invention, a non-transient computer readable storage device is provided comprising instructions which, when executed in the processor of an apparatus, perform the method detailed above.

In accordance with yet another aspect of the invention, a computer program is provided which, when executed in the processor of an apparatus, performs the method detailed above.

Brief description of the drawings

Other features and advantages of the invention will readily appear from the following description of one of its embodiments, provided as non-limiting examples, and from the accompanying drawings.

In the drawings:

- Figure 1 is an illustration of an apparatus according to an embodiment of the invention;

- Figure 2 is a flow chart of a method according to an embodiment of the invention.

- Figures 3a, 3b and 3c are illustrations of mobile robots according to embodiments of the invention in different environments;

In the different figures, the same reference signs designate the same or similar elements.

Detailed description

Reference will now be made in detail to embodiments of the invention described below, with reference to the attached figures. In this regard, the embodiments of the invention can be carried out in various ways and should not be construed as limited to the embodiments set forth below.

It will be understood that some embodiments of the invention, described hereafter in reference to flowcharts or block diagrams, can be implemented by computer-readable instructions. These computer-readable instructions can be provided to the processor of a general purpose computer, a specific purpose processor or computer, or other programmable data circuit such that the instructions executed by the processor or circuit create modules that implement operations and stages specified in the flowchart blocks.

Thus, the embodiments of the present invention can be implemented through a non-transient computer readable storage device comprising any means or means that allow for the storage and transmission of computer readable instructions or codes.

The computer-readable code may be recorded and transferred into a non-transient computer-readable storage device in known ways, and the device may include recording media, such as magnetic storage media and optical recording media. The storage device may include volatile and non-volatile memories. The storage device may also include elements of the Internet or a computer network. Therefore, the device can be a defined and measurable structure that carries or controls a signal or information, such as a device that carries a bit stream, for example, in accordance with the embodiments of the present invention. The non-transient computer readable storage device may also be a distributed network, so that the computer program is stored, transferred and executed from distributed form By way of example only, the processor may include a circuit or a computer processor, and the processing circuits may be distributed or included in a single circuit.

An apparatus 1 for determining reference elements of an environment 2 will be described below in reference to Figure 1.

Said apparatus 1 may comprise a distance measuring sensor 10, a processor or processing circuit 11 and a memory 12.

The distance measuring sensor 10 may, for example, include a laser rangefinder such as a LIDAR module (acronym for "light detection and ranging"), a radar module, an ultrasonic distance measurement module, a module sonar, a distance measurement module that uses triangulation or any other device capable of acquiring the distance or position of a single point or a plurality of surrounding points. In a preferred embodiment, a distance measurement sensor 10 is used which emits a physical signal emitted and receives a reflected physical signal. This distance measurement sensor then calculates a distance, which corresponds to the distance of the sensor to a single point or a plurality of points in the environment, comparing the emitted signal and the reflected signal, for example comparing the emission time and the time of reception.

The emitted and reflected signals can be, for example, light beams, electromagnetic waves or acoustic waves. Advantageously, a rangefinder 10 is used. This rangefinder 10 can scan the environment 2 of the apparatus 1 in a two-dimensional X, Y plane to acquire a set of observations Oi corresponding to a set of points of the environment, the points being indexed, for example, by a number i. Each observation Oi can comprise a distance Ri and a marking ai associated with a point in the environment.

The distance may correspond to a distance between the environment point and the distance measurement sensor 10, and the marking may correspond to an angle between the line that joins the environment point to the distance measurement sensor 10 and a direction comprised in the X, Y two-dimensional plane.

The two-dimensional X, Y plane can comprise a first X direction and a second non-collinear Y direction with the first X direction, said directions forming coordinate axes.

The distance measuring sensor 10 can for example scan the environment 2 by rotating around a third direction Z. The third direction can be perpendicular to the first and second directions, thereby allowing the sensor 10 to scan the environment 2 in said direction. plane X, Y two-dimensional and acquire observations corresponding to a set of points of the environment, said observations being acquired, for example, with regularly spaced markings.

In some embodiments, the distance measuring sensor 10 may consist of a laser that rotates around the third direction with a constant rotation speed and emits pulses of light at a constant time rate. The pulses of reflected light are collected by the distance measuring sensor 10 and the time difference between the emitted pulses and the received pulses can provide the range of the specific environment point.

The memory 12 is capable of storing a position P ^a of the device that can be estimated, for example in real time, or can be defined preliminary. This position may correspond to the position of the device 1 or the distance measuring sensor 10. This position may further comprise a first coordinate xa along the first direction X and a second coordinate yA along the second direction Y.

The processor 11 can transform, using simple trigonometric formulas, each observation Oi acquired by the laser rangefinder 10 at a position Pi of a point of the environment comprising two coordinates, a first coordinate xi along the first direction X and a second coordinate yi along the second direction Y, where said position Pi of a point of the environment is stored in memory 12.

The first X and the second Y addresses can correspond to any axis or direction of a coordinate system capable of defining the position of a point of the environment in at least two dimensions. They can correspond to directions or axes of a polar, cylindrical, spherical, or similar coordinate system.

They may, advantageously, correspond respectively to a horizontal and vertical direction of the environment 2. The third direction Z can then correspond to another horizontal direction, perpendicular to the first direction X. In the last example, a position Pi = (xi, yi ) of a point in the environment can simply be calculated from an associated Oi = (Ri, ai) observation and the position Pa = (xaJ a) of the device as

'xA Rcos {a )

⁽ⁱ⁾

xyA /?sen(«)

xyA /? sen («)

An illustration of an environment 2 is illustrated in Figure 1 comprising a wall 21 and a box 22. The wall 21 is a reference element of the environment 2 and the box 22 is a non-referential element of the environment 2. This illustration of a environment is provided by way of example only and it is understood that an environment can be any type of environment with which an apparatus according to the invention could be found. In particular, an environment can include a variety of objects and elements corresponding to the variety of objects that can be seen in natural and artificial environments.

Additional illustrations of environments 2 are provided in Figures 3a, 3b and 3c together with embodiments of a robot 3 comprising an apparatus 1.

Referring to Figure 3a, a robot 3 may comprise the above-mentioned apparatus 1 in addition to additional modules.

As illustrated in the embodiment of Figure 3a, the robot 3 may include a frame 13 and a plurality of wheels or tread 14.

In some embodiments, the wheels or treads 14 can be adapted to be motorized and the robot 3 can thus travel autonomously within the environment 2. The robot 3 can therefore be a mobile robot 3.

The robot 3 can also comprise one or more motors 15 connected to the wheels or treads 14 in addition to one or more batteries or power supply 16 and communication modules 17, capable of receiving and / or sending information with an external device of a user using a cable or wireless communications link.

In a further reference to Figure 2, 3a, 3b and 3c, a method for determining reference elements in environment 2 will be described below.

Said method may comprise a first stage 110 in which a ceiling value yC and a floor value yF are provided. These values may, for example, be provided by an operator who can be a human operator. These values can correspond respectively to a virtual or real roof 31 and a virtual or real floor 32 in the environment 2, as illustrated in Figure 1.

These values can be stored in the device memory 12.

These values could also be provided during subsequent stages 120, 130.

These values could also be determined by the apparatus 1 in real time or during subsequent stages.

In a second stage 120, one or several sets 40 of positions Pi of surrounding points are measured using the aforementioned distance measuring sensor 10, processor 11 and memory 12. The positions can be calculated from a set of observations Oi performed by the apparatus, as detailed above in reference to Figure 1. The operation of calculating positions from the observations can be performed using simple trigonometric formulas, such as formula (1).

As illustrated in Figure 3a, an assembly 40 may comprise positions Pi of points of the environment aligned along a straight line 41.

The straight line 41, for example, can be comprised within the two-dimensional X, Y plane.

The straight line 41 can also be aligned with the second direction Y.

As illustrated in Figure 3a, an assembly 40a may comprise positions Pi of points of the environment located in different elements of environment 2.

The assembly 40a may comprise points of the environment aligned along straight lines 41a.

In particular, a set 40a may comprise positions P¡ whose first x coordinates are separated from each other.

In some embodiments, the second yi coordinate of each position Pi of surrounding points may be limited so that it is between the ceiling value e and the floor value yF. Therefore, if a second yi coordinate of a position Pi of surrounding points is that the ceiling value e, this second coordinate yi can be replaced by the ceiling value e. Similarly, if a second yi coordinate of a position Pi of surrounding points is lower than the ceiling value e, this second yi coordinate can be replaced by the yF value of soil.

In a third stage 130, environment reference points and environment reference elements are determined. The determination step 130 may comprise various operations.

In a first operation 131, a set of interior point positions is defined.

The set of interior point positions is composed of point positions of the environment set of points whose second coordinate yi is strictly less than the ceiling value e and strictly greater than the floor value yF.

The second coordinates of the point positions belonging to the set of interior point positions are therefore strictly between the ceiling value e and the floor value yF.

If a second yi coordinate of a point of the environment Pi is equal to or greater than the value e of ceiling, respectively equal to or less than the value yF of soil, it is assumed that this point of the environment is part of the ceiling, respectively of the ground, and therefore it is not taken into consideration for the determination of non-referential elements of the environment.

In a second operation 132 a set of distances is calculated. For each position P¡ = ( ^x ¡, yi) of a point of the interior, a distance Di is calculated, taken along the first direction X, which separates said point from the interior of the apparatus 1 or of the measuring sensor 10 of distance.

This distance can, for example, be calculated from the position P¡ = (x¡, yi) of a point inside and from the position P ^a = (x ^a , yA) of the device using a formula such as D¡ = | x¡ -x ^a |.

A distance, taken along one direction, between two points is a distance between two respective projections of said two points in said direction. Said distance can therefore be calculated from the coordinates of the positions of said two points.

In an embodiment of the invention in which the first and second directions correspond to an axis of a polar, cylindrical, spherical coordinate system, the formula used to calculate the distance can be more elaborated and would be determined accordingly by an expert using mathematical formulas for distance. In a variant, the distance could be calculated on a plane comprising two directions, for example using a formula such as D¡ = ^ {xt - xA) 2 + (z¡ - zA) 2 in which z ^a is a third coordinate of the position P ^a of the device yz¡ is a third coordinate of the position P¡ of a point.

In a variant, the second operation could be performed on the set of points in the environment instead of the set of points inside.

In a third operation 133, a set of positions of environment reference points is identified.

This set of positions of reference points of the environment corresponds to positions of the set of positions of points of the interior, or the set of positions of points of the environment, whose distance is the distance in the set of distances.

A set of non-referential point positions of the environment can also be identified, which corresponds to positions of the set of interior point positions, or the set of position points of the environment, whose distance is not the distance in the set of distances.

Most non-referential elements have an extension, taken along the second direction, which is strictly smaller than the distance between the virtual roof and the virtual floor.

An item not reference! having an extension, taken along the second direction, strictly smaller than the distance that separates the virtual roof from the virtual floor, will therefore leave a finite open distance along the second direction Y free of obstacles.

This finite open distance can provide access to more distant elements of the environment, such as the wall 21, for the distance measuring sensor 10.

By way of illustration only, such non-referential elements may comprise boxes, cars, pallets, stored products and the like.

An environment comprising a box 22 is shown for example in Figure 3a in which a box 22 is placed for example in front of a wall 21.

The extension of the box 22 along the direction Y is strictly smaller than the distance between the virtual roof 31 and the virtual floor 32.

The box 22 will therefore be detected as a non-referential element, as will be explained in more detail below.

The extension of the wall 21 along the vertical Y direction is equal to or greater than the distance between the virtual roof 31 and the virtual floor 32.

The wall 21 will therefore be detected as a reference element, as will be explained in more detail below.

Various sets of positions 40 of interior points are illustrated in Figures 3a, 3b and 3c.

A set of positions 40a of interior points, taken along the vertical line 41, may comprise points around the wall 21a and points around the box 22a.

Because the box 21 is located in front of the wall 21 and because its extension, taken along the second direction Y, is strictly smaller than the distance between the virtual roof 31 and the virtual floor 32, some points around the wall 21a comprised in the set of positions 41a of interior points are located farther from the apparatus 1 than some points in the environment of the box 22a comprised in the set of positions 40a of interior points.

Consequently, the distance Di, taken along the first direction X, which separates said points from the environment of the wall 21a of the apparatus 1, or the distance measuring sensor 10, is that the distance Di which separates said points from the environment of the box 22a of the apparatus 1, or of the distance measuring sensor 10.

Because a set of positions of reference points of the environment corresponds to positions of the set of points of the interior, or the set of positions of points of the environment, whose distance is the distance in the set of distances, wall 21 is identified as A reference element.

Similarly, the points of the environment of the box 22a whose distances are not the greatest distances between the set of distances, are identified as positions of non-referential points of the environment.

Box 21 is therefore identified as a non-referential element of environment 2.

The present method thus provides a way to distinguish non-referential elements from reference elements with a high probability of success.

Referring to Figure 3b, an example of successful identification of a column 50 as a reference element of an environment 2 is illustrated.

Column 50 is placed in front of a wall 21 in the example of Figure 3b but it should be noted that said wall 21 is not required for the identification of column 50 provided the extension of column 50, taken along the second direction, equal to, or greater than, the distance that separates the virtual roof from the virtual floor. Figure 3c illustrates an environment 2 comprising an opening 60 in a first wall 61 located in front of a second wall 21 with respect to an apparatus 1.

The opening 60 separates two sets of points from the environment of the first wall 61 or two elements of the environment 2: a set of points 62a from the upper environment of the first wall, which belong to a first upper wall 62; and a set of points 63a from the lower surroundings of the first wall, which belong to a first lower wall 63.

Because the vertical extensions of these two sets of environmental points or two elements are strictly smaller than the distance between the virtual roof 31 and the virtual floor 32, these elements are identified as non-referential elements of environment 2.

The first upper wall 62 and the first lower wall 63 of an opening 60 are therefore identified as non-referential elements while they should be identified as reference elements.

It should be noted that a small number of false negative and / or false positive identifications is not detrimental to a good association of a predetermined map with a real-time environment map, and to the other advantages detailed above.

The location of the virtual roof and the virtual floor can be adjusted by setting values for the yC value of the ceiling and the yF value of the floor that fit the environment of the embodiment of the invention.

The yC value of the roof and the yF value of the floor respectively define the location of the virtual roof and the virtual floor along the second direction.

In some embodiments of the invention, the first coordinate of the set of environment positions may be grouped or quantified with a first grouping interval.

Therefore, the first coordinates that fall within an interval whose width is equal to the first grouping interval are replaced by a representative value of that interval. This value may be the central value of the interval or an arbitrary index indicating that interval.

In this way, the deviations of some point alignments from the environment of the first direction can be compensated. These deviations can arise, for example, from uncertainties in the measurements or inclinations of the elements in the environment.

The second coordinate of the set of positions in the environment can also be grouped or quantified with a second grouping interval.

In this way, the deviations of some alignment of points of the environment from the second direction can be compensated. These deviations can arise, for example, from uncertainties in the measurements or inclinations in the environment.

In another embodiment, the positions may comprise a third coordinate along a third direction, not collinear with the first and second directions.

It should be noted that the specific order of the operations set forth above could be changed without departing from the invention.

Part of the previous operations could also be combined into single operations.

The order of the steps described above could also be exchanged in some embodiments without departing from the invention.

In particular, the first stage 110 of providing a ceiling value yC and a floor value yF could be carried out during and after the second measurement stage 120 or during or after the third determination stage 130.

The first stage 110 could be repeated several times to adapt the yC value and the yF value of the soil to the positions of the measured environment points.

It could be repeated during and after the second measurement stage 120 or during or after the third determination stage 130.

The stages described above could be combined with each other in fewer stages.

Various operations of the third stage 130 of determination could be performed during the second stage 120 of measurement.

For example, the first operation of the third stage 131, which comprises the definition of a set of interior point positions, can be performed directly during the second measurement stage 120.

The calculation of the distance set, performed in the second operation of the third stage 132, could also be performed during the second stage 120.

Although various aspects of the invention have been described in particular details, and with reference to specific embodiments, it should be understood that these embodiments are not to be considered as limiting the scope of the present invention.

Claims (14)

1. A method for determining reference elements of an environment to associate a predetermined map with a real-time environment map, the method comprising at least the steps of: - providing a ceiling value and a floor value, these values corresponding respectively to a virtual or real roof (31) and a virtual or real floor (32) in the environment (2); - measuring, using a distance measuring sensor (10), sets (40) of positions of surrounding points, each of said positions comprising at least a first coordinate along a first direction (X) and a second coordinate along a second direction (Y) not collinear with the first direction (X), where each set (40) of positions of surrounding points is aligned along a straight line (41); - determining reference elements and non-referential elements of the environment, each reference element comprising a set of positions of environment reference points, said set of environment point positions comprising at least one position of a set (40) of positions of environment points * whose second coordinate is strictly less than the ceiling value and strictly greater than the floor value, and * whose distance to the distance measurement sensor, taken along the first direction, is the greatest distance in a set of distances from said a set (40) of surrounding points to the distance measurement sensor, where said distances are taken along the first direction (X), said non-referential elements corresponding to positions of a set (40) of positions of surrounding points, whose distance to the distance measuring sensor, taken along the first direction (X), is not the greatest distance in a set of distances from said a set of points of the environment to the distance measurement sensor, where said distances are taken along the first direction (X). 2. The method according to claim 1, wherein the first and second directions (X, Y) are perpendicular, said second direction (Y) corresponding to a vertical direction of the environment. 3. The method according to claim 1 or claim 2, wherein the determination step comprises at least the operations of: - define a set of interior point positions comprising positions of each set of environment point positions whose second coordinate is strictly less than the ceiling value and strictly greater than the floor value, - calculate, for each point position in said set of interior point positions, a distance, taken along the first direction, which separates said point from the distance measuring sensor, to obtain said set of distances; - identifying said set of positions of reference points of the environment corresponding to positions of a set of positions of interior points whose distance is the greatest distance from the set of distances, - identify said non-referential elements corresponding to positions of a set of interior point positions, whose distance to the distance measurement sensor, taken along the first direction, is not the greatest distance in a set of distances of said a set of points from the inside to the distance measurement sensor, where said distances are taken along the first direction. 4. The method according to any of the preceding claims, wherein said straight line (41) is aligned with the second direction (Y). 5. The method according to any of the preceding claims, wherein the distance measuring sensor (10) comprises a laser. 6. The method according to any of the preceding claims, wherein the first coordinates of a set of point positions are grouped with a first crush interval. 7. The method according to any of the preceding claims, wherein the second coordinates of a set of point positions are grouped with a second grouping interval. 8. An apparatus for determining reference elements of an environment to associate a predetermined map with a real-time environment map, the apparatus comprising: - a distance measuring sensor (10) for measuring sets (40) of positions of surrounding points, each of said positions comprising at least a first coordinate along a first direction (X) and a second coordinate at along a second direction (Y) not collinear with the first direction (X), where each set (40) of positions of surrounding points is aligned along a straight line (41); - a memory for storing a provided ceiling value, a provided floor value, these values corresponding respectively to a virtual or real roof (31) and a virtual or real floor (32), and for storing said sets of point positions of the environment; - a processor for determining reference elements and non-reference elements of the environment, each reference element comprising a set of positions of reference points of the environment corresponding to positions of a set of position points of the environment * whose second coordinate is strictly less than the ceiling value and strictly greater than the floor value, and * whose distance to the distance measurement sensor, taken along the first direction, is the greatest distance in a set of distances from said a set (40) of surrounding points to the measurement sensor, where said distances are take along the first direction (X), said non-referential elements corresponding to positions of a set (40) of positions of surrounding points, whose distance to the distance measuring sensor, taken along the first direction (X), is not the greatest distance in a set of distances from said a set (40) of points of the environment to the distance measuring sensor (10), where said distances are taken along the first direction (X). 9. The apparatus according to claim 8, wherein the first and second directions (X, Y) are perpendicular, said second direction (Y) corresponding to a vertical direction of the environment. 10. The apparatus according to claim 8 or claim 9, wherein the distance measuring sensor (10) comprises a laser. 11. The apparatus according to any of claims 8 to 10, wherein said straight line (41) is aligned with the second direction (Y). 12. A mobile robot comprising the apparatus according to any of claims 8 to 11. 13. Non-transient computer readable storage device comprising instructions which, when executed in a processor of an apparatus according to any of claims 8-11, perform the method according to any of claims 1 to 7. 14. Computer program which, when executed in a processor of an apparatus according to any of claims 8-11, performs the method according to any of claims 1 to 7.